Porous metal-organic frameworks with Lewis basic nitrogen sites for high-capacity methane storage

The use of porous materials to store/deliver natural gas (mostly methane) in vehicles requires large amounts of methane being stored per unit volume. In this work, we report several porous metal-organic frameworks (MOFs) with NOTT-101 type structures, containing Lewis basic nitrogen sites through the incorporation of pyridine, pyridazine, and pyrimidine groups into the organic linkers. They exhibit significantly higher total volumetric methane storage capacities (similar to 249-257 cm(3) (STP) cm(-3) at room temperature (RT) and 65 bar) than NOTT-101a (here the MOF abbreviation with "a'' at the end represents the fully activated MOF). The most significant enhancement was observed on UTSA-76a with functional pyrimidine groups (237 cm(3) (STP) cm(-3) in NOTT-101a vs. 257 cm(3) (STP) cm(-3) in UTSA-76a). Several multivariate (MTV) MOFs constructed from two types of organic linkers (pyrimidine-functionalized and unfunctionalized) also show systematically improved methane storage capacities with increasing percentage of functionalized organic linkers. The immobilized functional groups have nearly no effect on the methane uptakes at 5 bar but significantly improve the methane storage capacities at 65 bar, so the reported MOFs exhibit excellent methane storage working capacities of similar to 188-197 cm(3) (STP) cm(-3).